The quilt patch titled Subject: mm: list_lru: fix UAF for memory cgroup has been removed from the -mm tree. Its filename was mm-list_lru-fix-uaf-for-memory-cgroup.patch

This patch was dropped because it was merged into the mm-hotfixes-stable branch of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

------------------------------------------------------ From: Muchun Song songmuchun@bytedance.com Subject: mm: list_lru: fix UAF for memory cgroup Date: Thu, 18 Jul 2024 16:36:07 +0800

The mem_cgroup_from_slab_obj() is supposed to be called under rcu lock or cgroup_mutex or others which could prevent returned memcg from being freed. Fix it by adding missing rcu read lock.

Found by code inspection.

[songmuchun@bytedance.com: only grab rcu lock when necessary, per Vlastimil] Link: https://lkml.kernel.org/r/20240801024603.1865-1-songmuchun@bytedance.com Link: https://lkml.kernel.org/r/20240718083607.42068-1-songmuchun@bytedance.com Fixes: 0a97c01cd20b ("list_lru: allow explicit memcg and NUMA node selection") Signed-off-by: Muchun Song songmuchun@bytedance.com Acked-by: Shakeel Butt shakeel.butt@linux.dev Acked-by: Vlastimil Babka vbabka@suse.cz Cc: Johannes Weiner hannes@cmpxchg.org Cc: Nhat Pham nphamcs@gmail.com Cc: stable@vger.kernel.org Signed-off-by: Andrew Morton akpm@linux-foundation.org ---

mm/list_lru.c | 28 ++++++++++++++++++++++------ 1 file changed, 22 insertions(+), 6 deletions(-)

--- a/mm/list_lru.c~mm-list_lru-fix-uaf-for-memory-cgroup +++ a/mm/list_lru.c @@ -85,6 +85,7 @@ list_lru_from_memcg_idx(struct list_lru } #endif /* CONFIG_MEMCG */

+/* The caller must ensure the memcg lifetime. */ bool list_lru_add(struct list_lru *lru, struct list_head *item, int nid, struct mem_cgroup *memcg) { @@ -109,14 +110,22 @@ EXPORT_SYMBOL_GPL(list_lru_add);

bool list_lru_add_obj(struct list_lru *lru, struct list_head *item) { + bool ret; int nid = page_to_nid(virt_to_page(item)); - struct mem_cgroup *memcg = list_lru_memcg_aware(lru) ? - mem_cgroup_from_slab_obj(item) : NULL;

- return list_lru_add(lru, item, nid, memcg); + if (list_lru_memcg_aware(lru)) { + rcu_read_lock(); + ret = list_lru_add(lru, item, nid, mem_cgroup_from_slab_obj(item)); + rcu_read_unlock(); + } else { + ret = list_lru_add(lru, item, nid, NULL); + } + + return ret; } EXPORT_SYMBOL_GPL(list_lru_add_obj);

+/* The caller must ensure the memcg lifetime. */ bool list_lru_del(struct list_lru *lru, struct list_head *item, int nid, struct mem_cgroup *memcg) { @@ -139,11 +148,18 @@ EXPORT_SYMBOL_GPL(list_lru_del);

bool list_lru_del_obj(struct list_lru *lru, struct list_head *item) { + bool ret; int nid = page_to_nid(virt_to_page(item)); - struct mem_cgroup *memcg = list_lru_memcg_aware(lru) ? - mem_cgroup_from_slab_obj(item) : NULL;

- return list_lru_del(lru, item, nid, memcg); + if (list_lru_memcg_aware(lru)) { + rcu_read_lock(); + ret = list_lru_del(lru, item, nid, mem_cgroup_from_slab_obj(item)); + rcu_read_unlock(); + } else { + ret = list_lru_del(lru, item, nid, NULL); + } + + return ret; } EXPORT_SYMBOL_GPL(list_lru_del_obj);

_

Patches currently in -mm which might be from songmuchun@bytedance.com are

mm-kmem-remove-mem_cgroup_from_obj.patch